1. Field of the Invention
The present invention relates to a method for improvement of extracorporeal excretion of potassium ion and inducing decrease in potassium ion concentration in the blood which comprises administering a prostanoic acid derivative to a subject.
The object of the present invention is to reduce potassium ion concentration in the blood or improve extracorporeal excretion of potassium ion in the treatment of conditions wherein potassium ion concentration in the blood is increased, e.g. hyperkalemia or renal insufficiency. Generally, potassium ion in the blood is excreted into the urine through the kidneys. According to the present invention, however, potassium ion is excreted through the intestinal wall as an alternative main route, and this route is effective for a patient whose renal function is reduced or injured. This method of excretion may be called "intracorporeal dialysis".
Renal insufficiency refers to a condition in which renal function is injured by renal diseases such as glamerulonephritis, nephrotic syndrome, nephrosclerosis, renal carcinoma, lupus nephritis etc. One important parameter for renal insufficiency is the excreting function of kidney and especially the concentration of potassium ion in the blood which are pooled in the body by injured excretion. Symptom of hyperkalemia appears as the pooling progresses.
Traditional means effective in the treatment of renal insufficiency is the so-called dialysis in which the blood is contacted with a dialysate with a semipermeable membrane between them whereby substances in the blood may be removed through diffusion by osmotic gradient. The dialysis include hemokialysis in which the arterial blood is introduced into an artificial kidney and returned to a vein and peritoneal dialysis in which blood substances are dispersed into a dialysate, which is introduced into the peritoneal cavity and discharged periodically, through capillary vessels serving as a semipermeable membrane. However, the former has disadvantage that it requires a sergical operation such as shunt operation while the latter has disadvantages that it has inferior dialysis efficacy and requires infection-preventing measures.
2. Background Information
The present invention and co-workers formerly discovered that 15-keto-16-halo-prostaglandins (hereinafter, prostaglandin is referred to as PG) have an enteropooling activity (activity of pooling water in intestines) (EP-A-310305). Enteropooling activity of 16,16-dimethyl-PGE.sub.2 has also been described in Prostaglandins, 11, 809-828(1976). However, nothing has been reported about the fact that prostanoic acid derivatives have activity of excreting potassium ion.
As a result of extensive studies about the properties of PG compounds, the present inventors unexpectedly discovered that these compounds have an activity of decreasing potassium ion concentration in the blood and excreting potassium ion.